An electric vehicle (EV), also referred to as an electric drive vehicle, uses an electric motor (or traction motor) for propulsion. Electric vehicles may include all-electric vehicles where the electric motor is the sole source of power, and hybrid electric vehicles that include an auxiliary power source in addition to the electric motor. In an electric vehicle, energy may be stored in one or more batteries (located in the electric vehicle) to power the electric motor. When the stored energy decreases, the batteries may be charged (or recharged) by connecting the vehicle to an external power supply. Although the current disclosure is applicable, without limitations, to any type of electric vehicle, an exemplary case of an electric bus will be described to illustrate the features of the disclosed system.
For a given weight of the bus, the number, chemistry, and architecture of the battery assembly may determine the distance the bus can travel between recharges (range) and the time it takes to recharge the batteries (recharge time). For some applications, (for example, transit buses) where quick charging is important, fast-charge battery systems may be employed. Fast-charge batteries may store a relatively small amount of charge, but may be charged to substantially full capacity quickly. Battery system architecture may also allow fast charging of non-fast charge batteries. Some exemplary fast-charge battery systems suitable for an electric bus are described in commonly assigned U.S. Pat. No. 8,453,773 which is incorporated herein by reference in its entirety.
Because the range of a fast-charge electric bus is low, these buses are typically recharged along its route. In some applications, charging stations may be provided at a bus stop or another layover location to recharge the bus without inconveniencing passengers. At these charging stations, the electric bus couples with an arm or other mechanism of the charging station to direct external electric power to the bus to recharge the batteries. Typically, the cost of energy in a geographic area (city, county, etc.) varies as a function of, among other factors, the season (summer, winter, etc.), time of day (peak time, off-peak time, etc.), the rate of energy consumption (power), etc. When a fleet of electric buses operate in the area, energy cost may be a substantial portion of the total operating cost of the buses. Significant savings in energy cost may be achieved by controlling the recharging of the buses in the fleet based on the energy rates and the state of charge of all the buses in the fleet.